Investigations for the diagnostic recording of nasal wing collapse.

BACKGROUND: The inspiratory medial movement of the nasal wing at high flow velocities is a protective physiologic mechanism. If this collapse of the nasal wing occurs at lower flow velocities, it may result in nasal obstruction. "Nasal wing collapse" is generally a clinical diagnosis. However, in the pressure-flow relationship of rhinomanometry, the medial movement of the nasal wing can be documented in the inspiratory arm of the graph. The diagnostic impact of this hysteresis was investigated.

METHODS: The pressure-flow curves of three box models and three nasal models with a moveable valve (analogous to the nasal wing) in the entrance area as well as three volunteers with unstable nasal wings were investigated. We recorded synchronously the pressure-flow relationship and by endoscopy the movement of the valve in the box models and the nasal wing in the volunteers on video. For evaluation, we used the frame by frame analysis of the tape.

RESULTS AND CONCLUSIONS: The medial movement of the nasal wing causes a hysteresis in the inspiratory arm of the pressure-flow curve. At this point, the graph runs on or between two border curves, termed the "no collapse curve" (for the maximally opened valve or a stable nasal wing) and the "collapse curve" (for the subtotally closed valve or a collapsed nasal wing), respectively. Analogous to the nasal wing motion, the descending course of hysteresis runs in two phases, and the ascending course runs in three phases. The medial movement of the nasal wing is expressed by a deviation of the graph from the "no collapse curve." The flow, at which the graph leaves this curve, depends on the elasticity module of the nasal wing. The extent of nasal wing collapse is reflected by the approximation of the pressure-flow curve to the "collapse curve" of the graph. The hysteresis appears because of a late opening of the collapsed nasal wing.